• 대한기계학회논문집B
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• 제25권12호
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• pp.1887-1897
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• 2001

Korea Atomic Energy Research Institute (KAERI) launched an intermediate scale steam explosion experiment named "Test for Real Corium Interaction with water (TROI)" using reactor material to investigate whether the molten reactor material would lead to energetic steam explosion when interacted wish cold water at low pressure. The melt-water interaction experiment is performed in a pressure vessel with the multi-dimensional fuel and water pool geometry. The novel concept of cold crucible technology, where powder of the reactor material in a water-cooled cafe is heated by high frequency induction, is firstly implemented for the generation of molten fuel. In this paper, the lest facility and cold crucible technology are introduced and the results or the first series of tests were discussed. The 5 kg of molten ZrO$_2$jet was poured into the 67cm deep water pool at 30 ∼ 95 $\^{C}$. Either spontaneous steam explosions or quenching was observed. The morphology of debris and pressure wave profiles clearly indicate the differences between the two cases.

• 한국압력기기공학회 논문집
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• 제14권2호
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• pp.1-10
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• 2018

Structures, systems and components of nuclear power plants should be able to maintain safety even in the event of design-basis accidents such as high-energy line breaks. The high-pressure steam jet ejected from the broken pipe may cause damage to the adjacent structures. The ANSI/ANS 58.2 code has been adopted as a technical standard for evaluating the jet impingement load. Recently, the U.S. NRC pointed out the non-conservativeness of the ANSI/ANS 58.2, because it does not take into account the blast wave effect, dynamic behavior of the jet, and oversimplifies the shape and load characteristics of the supersonic steam jet. Therefore, it is necessary to improve the evaluation method for the high-energy line break accident. In order to evaluate the behavior of supersonic steam jet, an appropriate numerical analysis technique considering compressible flow effect is needed. In this study, numerical analysis methodology for evaluating supersonic jet impingement load was developed and verified. In addition, the conservativeness of the ANSI/ANS 58.2 model was investigated using the numerical analysis methodology. It is estimated that the ANSI jet model does not sufficiently reflect the physical behavior of under-expanded supersonic steam jet and evaluates the jet impingement load lower than CFD analysis result at certain positions.

• 한국전산유체공학회지
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• 제20권3호
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• pp.87-93
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• 2015

In this study, a numerical analysis was performed to simulate the thermal-hydraulic response of the secondary side of a steam generator(SG) model equipped with an orifice-type SG outlet flow restrictor to a main steam line break(MSLB) at a pressurized water reactor(PWR) plant. The SG analysis model includes the SG upper steam space and the part of the main steam pipe between the SG outlet and the broken pipe end. By comparing the numerical calculation results for the present SG model to those obtained for a simple SG model having no flow restrictor, the effects of the flow restrictor on the thermal-hydraulic response of SG to the MSLB were investigated.

• 대한기계학회논문집B
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• 제33권1호
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• pp.60-68
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• 2009

The steam reformer for hydrogen production from methane is studied by a numerical method. Langmuir- Hinshelwood model is incorporated for catalytic surface reactions, and the pseudo-homogeneous model is used to take into account local equilibrium phenomena between a catalyst and bulk gas. Dominant chemical reactions are Steam Reforming (SR) reaction, Water-Gas Shift (WGS) reaction, and Direct Steam Reforming (DSR) reaction. The numerical results are validated with experimental results at the same operating conditions. Using the validated code, parametric study has been numerically performed in view of the steam reformer performance. As increasing a wall temperature, the fuel conversion increases due to the high heat transfer rate. When Steam to Carbon Ratio (SCR) increases, the concentration of carbon monoxide decreases since WGS reaction becomes more active. When increasing Gas Hourly Space Velocity (GHSV), the fuel conversion decreases due to the heat transfer limitation and the low residence time. The reactor shape effects are also investigated. The length and radius of cylindrical reactors are changed at the same catalyst volume. The longer steam reformer is, the better steam reformer performs. However, system energy efficiency decreases due to the large pressure drop.

• 수산해양기술연구
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• 제53권3호
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• pp.302-307
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• 2017

An electric steam boiler equipped with a condensate recovery system, which stores the condensate generated after using steam in steam washers, steam cookers, steam irons, and steam cleaners in a condensate tank and supplies compressed air to the condensate tank so that the condensate is recovered to the boiler by the pressure of the compressed air, was studied. In the results of this study, the heat energy balance between the quantity of the heat generated by the non-metallic surface heating element and the quantity of the heat absorbed by the water was good in a range of ${\pm}5%$. In addition, the heat transfer rate increased in proportion to the electric power of the surface heating element heater, the waste heat energy was normally recovered by the recovery of the condensate of the steam boiler equipped with the high compression waste heat recovery system, and the recovery rate of the waste heat exhibited 23%.

• 비파괴검사학회지
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• 제26권1호
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• pp.12-17
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• 2006

원자력발전소의 증기발생기는 수천 개의 매우 얇은 두께의 튜브로 구성되어 있다. 이러한 증기발생기의 튜브는 원자력발전소의 1차 계통과 2차 계통의 압력경계를 유지하는 데에 매우 중요한 역할을 하고 있으며, 고온 고압의 열 수력적 상호작용으로 인한 가혹한 운전조건으로 인하여 손상되기 쉽다. 따라서 증기발생기의 구조적 건전성을 평가하기 위하여 많은 시간과 노력이 투입되고 있다. 와전류 검사 방법이 증기발생기 튜브의 건전성을 평가하기 위한 가장 보편적인 비파괴 방법이지만, 와전류 검사의 특성상 결함의 전체 체적에 의하여 신호의 특성이 나타나게 되어 정확한 결함의 크기를 평가하기에는 한계가 있다. 본 연구에서는 증기발생기 튜브의 결함 검출과 정확한 측정을 위하여 초음파 검사기법의 적용 가능성을 확인하였으며, 연구결과를 증기발생기 튜브 검사에 적용 할 경우 검사결과가 크게 향상 될 것으로 기대된다.

• KEPCO Journal on Electric Power and Energy
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• 제2권3호
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• pp.403-407
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• 2016

In general, drum-type boilers are designed for base load duty and applied under constant pressure operation mode. Recently, however conditions often occur that even drum-type boilers have to operate at partial load conditions. A feasibility study on adopting the sliding pressure operation for drum-type boiler was conducted, and corresponding performance changes and effects on the equipment were analyzed by utilizing a process simulation model. As a result, the conclusion was reached that drum type boilers are able to adopt the sliding pressure operation and can improve of net efficiency at part load operation in spite of the Rankine cycle efficiency reduction due to the decreases in main steam pressure. Because of thank to improvement of high pressure turbine stage-1 internal efficiency and power savings of boiler feed water pump. The sliding pressure operation is advantageous in terms of stress level relief for boiler tube as well as maintaining the rating steam temperature at part load condition. However, cautions are required because the drum boilers have poor dynamic response characteristics which may get worse during the sliding pressure operation.

• Nuclear Engineering and Technology
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• 제26권1호
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• pp.1-8
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• 1994

중대사고시 고온·고압의 열수력적 현상과 증기의 억제효과를 정량화할 수 있는 수소연소에 의한 화염속도 상관식을 제시하고 보정인자들을 정의하였다. 이 상관식은 기존의 Iijima-Takeno 상관식에 중대사고시에 예상되는 수소와 증기의 농도 범위에서 증기의 억제효과를 정량화하는 인자인 증기억제율을 정의하여 추가하고, 초기 압력의 영향을 고려하는 보정효과를 변형한 것이다. 또한 기존의 화염속도 모델은 상온·대기압력에서 수행된 실험에 기초한 상관식으로 중대사고시의 고온·고압의 열수력적 현상을 올바로 모사할 수 없으며. 증기의 억제 효과를 정량화할 수 없었다. 따라서 화염의 구조를 정의하고, 해석적 분석을 통해 화염속도를 계산하였고, 이 결과를 중대사고 해석용 코드인 MAAP, HECTR의 상관식 결과와 FITS 실험자료와 비교하여 해석적 모델의 적합성을 검증하였다. 이러한 결과를 기초로 화염 속도에 대한 증기의 억제 효자를 정량화하고, 초기 온도와 압력의 영향을 보정하는 인자들을 결정하여 수소연소에 의한 간편한 형태의 화염속도 상관식을 제시하였다.

• 한국소음진동공학회논문집
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• 제13권5호
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• pp.400-408
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• 2003

This paper investigates the vibration characteristics of steam generator (SG) U-tubes with defect. The operating SG shell-side flow field conditions for determining the fluidelastic instability parameters such as added mass are obtained from three-dimensional SG flow calculation. Modal analyses are performed for the U-tubes either with axial or circumferential flaw with different sizes. Special emphases are on the effects of flaw orientation and size on the modal and instability characteristics of tubes, which are expressed in terms of the natural frequency, corresponding mode shape and stability ratio. Also, addressed is the effect of the internal pressure on the vibration characteristics of the tube.

• 한국압력기기공학회 논문집
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• 제6권1호
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• pp.1-8
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• 2010

The existing maintenance program is focused on time-based maintenance to inspect and repair components according to maintenance period, rather than condition-based maintenance or predictive maintenance. The preventive maintenance template of the steam turbine has been developed for optimizing maintenance procedure and improving reliability and availability of the steam turbine of nuclear power plants based on EPRI PM template methodology and EPRI technical reports about preventive maintenance.